Method of extinguishing metal fires



United States Patent 2,787,329 METHOD OF EXTINGUISI'IING METAL FIRESWilliam H. Seheehter Zelienople, Pa, by m to, to Gallery ChemicalCompany, ilttsburgh, Pm, a corporation of Pennsylvania No Drawing.Application January 10, 1955,

Serial No. 481,030

6 Claim. (Cl. 169-1) This invention relates to new and usefulimprovements in methods of extinguishing metal fires and moreparticularly to the use of a trialkoxyboroxine, such astrimethoxyboroxine, BsOs(OCHs)s, for extinguishing fires of highlyinflammable metals such as sodium, lithium, potassium, magnesium andaluminum.

Three ingredients are necessary before it is possible to have a fire.These are fuel, heat, and an oxidizing agent such as air, oxygen, oroxidizing chemical compounds. A fire with active metals such as thealkali metals or magnesium or aluminum is no difierent than any otherfire in this respect and it is necessary to remove only any one of thethree ingredients to extinguish the fire. In most situations it isdiflicult to shut off the source of fuel to an active metal fire and itis therefore necessary to fight such fires by cutting off the source ofoxygen or reducing the temperature of the fire below the ignitiontemperature. In ordinary fires involving wood or simple organiccombustible materials the substance which is used to cut oil the supplyof oxygen (e. g. water) is also operable to reduce the temperature belowthe ignition point. In cases where it is not possible to use water asthe extinguishing agent other non-combustible materials such aschlorinated hydrocarbons and carbon dioxide are used to blanket acombustion area and cut off the supply of oxygen to the fire. In thecase of fires involving highly reactive metals none of theseextinguishing agents can be used. Water, chlorinated hydrocarbons, andcarbon dioxide all react readily with active metals at their flametemperatures to produce inflammable or poisonous by-products which aregaseous and will function to spread the fire over a much wider area. Ithas therefore been necessary in the past when attempting to extinguishfires in active metals to use a solid blanketing material such asanhydrous powdered talc or sodium carbonate or sand. Each of these solidextinguishing materials however must be completely dry to prevent theoccurrence of a violent reaction with the metal and also required theuse of equipment which can spread a dry powdered or granular materialover the area of the fire in suflicient concentration to blanket theburning material and cut off the supply of air to that material. Therehas therefore existed for some time a great demand for a liquid fireextinguishing medium for active metal fires which can be easily andsafely applied and which will act rapidly to extinguish such fires.

It istherefore one object of this invention to provide a new andimproved method for extinguishing fires in highly reactive metals whichuses a liquid extinguishing medium.

Another object of this invention is to provide a new and improved methodfor extinguishing fires in highly reactive metals in which the fire issupplied with a liquid or vaporized or atomized trialkoxyboroxine, suchas tri-- methoxyboroxine.

Another object of this invention is to provide a new and improved methodof extinguishing fires in highly reactive metals in which a liquidtrialkoxyboroxine, such as trimethoxyboroxine, is sprayed over thecombustion liquid trirnethoxyboroxine was sprayed into the combus-2,787,329 Patented Apr. 2, 1957 "ice 2 area in sutlicient quantity toprovide enough boric oxide to coat the inflammable metal and extinguishthe tire.

Other objects of thisinvention will become apparent from time to timethroughout the'specifieation and claims as hereinafter related.

This invention comprises a new and improved process for extinguishingfires in highly reactive metals which will be described more fullyhereinafter and the novelty of which will be particularly pointed outand distinctly claimed.

This invention is based upon my discovery that a trialkoxyboroxine, suchas trimethoxyboroxine,

when applied to a fire in an active metal will deposit large quantitiesof boric oxide on the metal surface and thus shut oil the supply ofoxygen to the fire and extinguish the fire. The most effective means ofextinguishing metal fires using trimethoxyboroxine is to spray theliquid into the combustion area. In the case of liquid metals such aslithium, sodium, potassium and alloys of these metals the only practicalmeans of applying the extinguishing liquid is to spray it into thecombustion area. In the case of solid metals, such as magnesium oraluminum it is also possible to extinguish the flame by projecting astream of liquid trimethoxyboroxine onto the surface of the burningmetal.

In one experiment a quantity of sodium was melted and ignited andallowed to burn vigorously. A quantity of tion area using a spray typefire extinguisher of the type used for spraying carbon tetrachloride.When the trimethoxyboroxine was sprayed into the combustion area therewas a flash of green flame as the trimethoxyboroxine burned to produce afinely divided boric oxide smoke which deposited as a glassy coating onthe surface of the sodium metal. The fire was almost instantlyextinguished.

In another experiment a quantity of magnesium turnings was ignited andallowed to burn vigorously. Trimethoxyboroxine was sprayed onto thisfire using the same apparatus as above described. As was described inconnection with the sodium fire the trimethoxyboroxine spray burst intoa green flame which immediately died out and left a glassy coating ofboric oxide on the magnesium turnings which immediately extinguished thefire. Other experiments together with known data relative to theunrcactivity of boric oxide toward activev metals has shown that thisprocess for extinguishing active metal fires is operative for all of thealkali metals, as well as for magnesium and aluminum. This process isalso operative where the extinguishing liquid is trimethoxyboroxinecontaining either additional quantities of dissolved boric oxide ordiluted with trimethyl borate. The p ocess is also operative where theextinguishing liquid is any other trialkoxyboroxine which is liquid atroom temperature, such as triethoxyboroxine, BaO3(OC2H5)a, ortripropoxyboroxine, BaOa(OCsl-l1)a.

Although there has been described herein only one embodiment of thisinvention it will be obvious to those skilled in the art that within thescope of the claims appended hereto this invention may be practicedotherwise than as specifically described.-

Having thus described my invention what I desire to claim and secure byLetters Patent of the United States is:

l. A method of extinguishing active metal fires which comprisesprojecting a trialkoxyboroxine onto the fire.

2. A method according to claim 1 in which the trialkoxyboroxine istrimethoxyborox'ine, BaOs(OCHa)a.

3. A method according to claim 2 in which the quantity oftrimethoxyboroxine projected onto the fire is sufiicient to generatesufficient boric oxide to substantially coat the surface of the burningmetal.

4. A method according to claim! in which thl: active -l References Citedin the tile of this patent metal is of the group consisting alkali metamagnesium, and aluminum UNITED STATES PATENTS 5. A method according toclaim 4 in which the tri- 3539 Rock Qt 909 methoxyboroxinc is sprayedonto the fire. 5 13131357 P y 31 6. A method according to claim 4 inwhich the metal is a solid and the trimethoxyboroxine iaprojectcd as astream.

1. A METHOD OF EXTINGUISHING ACTIVE METAL FIRES WHICH COMPRISES PROJECTING A TRIALKOXYBOROXINE ONTO THE FIRE. 